With significant advances in inkjet technology in recent years, it is becoming possible for inkjet image forming devices to produce large color prints of high quality at high speeds. Inkjet image forming devices are capable of producing prints by forming a number of ink dots on a recording medium by ejecting droplets of a plurality of inks, e.g., C, M, Y, K inks, onto the recording medium. Inkjet image forming devices are used widely, particularly in sign and display applications, and are applicable to, for example, prints on POP (Point Of Purchase) posters, wall posters, outdoor advertisements, billboards, etc. There are a wide variety of content types to be presented as prints, which include not only text, but also natural images, illustrations, graphs, computer graphics, etc. Various image processing technologies have been proposed in the art for identifying a content type from local features represented by an input image signal, and performing a color conversion process suitable for the identified content type.
Japanese Patent No. 4197346 discloses an apparatus for and a method of identifying character/halftone areas (or base/print sheet areas) from a relationship between densities in blocks, each of which is made up of a plurality of pixels, and selecting LUTs (Look Up Tables) suitable for the identified areas.
Japanese Laid-Open Patent Publication No. 08-065514 reveals an apparatus for and a method of separating and identifying character areas, photo areas, and halftone areas from input image data, and changing, in a stepwise and continuous manner, gradation characteristics that are suitable for the separated and identified areas.